*They have become so common that even organic retailer Whole Foods says it can't avoid stocking some

When a team of activists wearing white hazmat suits showed up at a Chicago grocery store to protest the sale of genetically modified foods, they picked an unlikely target: Whole Foods Market.

Organic foods, by definition, can't knowingly contain genetically modified organisms, known as GMOs. But genetically modified corn, soy and other crops have become such common ingredients in processed foods that even one of the nation's top organic food retailers says it hasn't been able to avoid stocking some products that contain them.

"No one would guess that there are genetically engineered foods right here in Whole Foods," said Alexis Baden-Mayer, political director of the Organic Consumers Association, which organized the protest. The activists dramatically trashed a battery of well-known health food brands outside the store, including Tofutti, Kashi and Boca Burgers.

Though people have been modifying foodstuffs through selective breeding and other methods for centuries, genetically modified crops differ in that the plants grow from seeds in which DNA splicing has been used to place genes from another source into a plant. In this way, the crop can be made to withstand a weed-killing pesticide, for example, or incorporate a bacterial toxin that can repel pests.

Some consumers are concerned that such changes may pose health risks and say manufacturers should be required to prove GMOs are safe for human consumption before putting them on the market. They also say products containing genetically modified ingredients should be identified for the consumer; the U.S. is one of the few industrialized nations that does not require such labeling or testing.

Industry representatives say that GMOs are safe and that labeling them is unnecessary, citing a 1992 statement from the FDA saying the agency had no reason to believe GMOs "differ from other foods in any meaningful or uniform way." No mainstream regulatory organization in the U.S. has opposed the introduction of GMOs.

"FDA has the scientific and nutrition expertise to establish food labeling and to assess food safety," said Ab Basu, the Biotechnology Industry Organization's acting executive vice president for food and agriculture. "You can look at the FDA website and see that if the corn is substantially equivalent to corn produced conventionally, there is no reason to label it as being any different."

Critics of the technology say they are concerned not only about possible health risks but also about soil and plant nutrient losses, contamination of non-GMO crops and increased pesticide use.

With an unprecedented number of genetically modified crops being greenlighted by the Obama administration in recent months amid public debate ”” including ethanol corn, alfalfa and sugar beets under certain conditions ”” some advocates say the issues may be reaching the awareness of consumers beyond the health-conscious shoppers who frequent Whole Foods.

They cite polls taken by the Pew Center, Consumers Union and Harris Interactive over the last decade that have consistently found the vast majority of Americans would like to see genetically modified foods better regulated and labeled.

"If companies say genetic engineering is fine, then OK let's label it and let the consumers make their own decisions," said Michael Hansen, a senior scientist at Consumers Union, which produces Consumer Reports. "That's what all the free market supporters say. So let's let the market work properly."

Michael Jacobsen, executive director for Center for Science in the Public Interest, which does not oppose GMOs, says many manufacturers see labeling as too risky. "No food company would use GMOs if they had to label them because there is no benefit to the companies," he said. "The term GMO has become a toxic term, and so if a company figures they will lose maybe 2 percent of their sales why should they? It's all loss for them."

In fact, a 2006 study for the Pew Initiative for Food and Biotechnology found that only 23 percent of women (the primary shopping decision makers) thought genetically modified foods were safe.

But knowledge on this topic also remains low. The same Pew study found that only 26 percent of American consumers believed they'd ever eaten genetically modified food, while a 2010 survey by the International Food Information Council reported that only 28 percent of respondents knew such foods were sold in stores.

Currently 14 states have introduced legislation on GMO labeling but most of it has not moved out of committee, including an Illinois bill introduced in February by Rep. Deborah Mell, D-Chicago. She says she plans to reintroduce it next session. Only Alaska, with its huge wild salmon industry, has passed a biotech seafood labeling law.

On the issue of safety, both sides of the debate come armed with research. This year Spanish researchers published an overview of GMO food safety studies in Environment International, finding that peer-reviewed studies had found health risks and no health risks in roughly equal numbers. The paper notes, however, that many studies finding no risks were sponsored by the biotech industry or associates.

Canadian researchers this year reported that the blood of 93 percent of pregnant women and 80 percent of their umbilical cord blood samples contained a pesticide implanted in GMO corn by the biotech company Monsanto, though digestion is supposed to remove it from the body. "Given the potential toxicity of these environmental pollutants and the fragility of the fetus, more studies are needed," they wrote in Reproductive Toxicology.

As the biggest producer of GMO seeds and the compatible pesticide Roundup, Missouri-based Monsanto is at the heart of the GMO debate. Monsanto would not make a representative available for an interview but did offer a statement on the lack of long-term animal or human safety studies on genetically modified crops.

"Experts in the field of food safety are satisfied that (the current) approach is sufficient and reliable to assure the genetically modified crops are as safe as their conventional counterparts," the statement said. "This expert community does not see a need and thus does not recommend long-term tests in humans or animals in order to establish food safety."

While the Food and Drug Administration has allowed the sale and planting of genetically modified foods for 15 years, it has never required premarket safety evaluations of the foods.

"Ultimately, it is the food producer who is responsible for assuring safety," the FDA wrote in a statement to the Tribune, noting that manufacturers are encouraged to consult with the agency about their products.

Used in an estimated 70 percent of all American processed food, genetically modified crops make up 93 percent of all soy, 86 percent of all corn and 93 percent of all canola seeds planted in the U.S., which makes stocking only non-GMO products difficult, said Joe Dickson, quality standards coordinator for Whole Foods Market.

"Until there's federal government mandated labeling of GMO ingredients, there's no way to tell if packaged products contain GMO ingredients," Dickson said. "Our approach is to work in the spirit of partnership with our suppliers ”¦ to encourage them to take active steps to avoid GMO ingredients."

Basu notes that GMO crops have been embraced by farmers in many countries ”” although not in Japan, Europe or Britain ”” and cites an International Food Information Council study that found 68 percent of those surveyed believe that FDA's current labeling practices are sufficient.

"If you look at the adoption of biotech by over 24 countries and over 2 billion acres of biotech crops globally that have been grown in the last 15 years of commercialization, consumers are buying these products," he said.

Still, Nielsen announced last year that "non-GMO" was the fastest-growing health and wellness claim on store-brand foods in 2009, up by 67 percent from the previous year and representing $60.2 million in sales.

And 2010 brought a new "Non-GMO Project Verified" seal, offering third-party certification that less than 0.9 percent of the ingredients in the product came from genetically modified organisms. More than 4,000 products ”” including all Whole Foods store brands ”” have been enrolled in the program, according to executive director Megan Westgate.

Shoppers at Whole Foods last week were conflicted about whether the store should be selling genetically modified foods. But the majority said they were surprised to find it did.

"It's disappointing and disheartening. I feel like Whole Foods has established itself as a community for people who believe in healthy food and I feel like they embody that. So I would think that they would uphold standards and prevent foods like this from being sold here," said Melissa Hayes, of Chicago.

"But I don't think it's fair to just blame Whole Foods," she added. "I think it's equally important for the consumer to take an active role and find out information on GMOs and Monsanto. Every time you make a purchase it's a vote and people just need to be more conscious and aware."

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If you want to avoid GMOs

Several shopping guides have been published in recent years offering vetted lists of products that do or don't contain biotech ingredients. They include the Non-GMO Shopping Guide, the Greenpeace Shoppers Guide and an iPhone app from the Non-GMO Project.

They also offer general guidance on avoiding GMO foods, including:

”¢Look for the Non-GMO Project Verified seal, which is the only third-party-tested verification program in the U.S.

”¢Choose certified organic foods, which cannot contain genetically modified ingredients or feed (for animals) as part of their certification.